GNU bug report logs - #10655
[2.0.3+] ‘queue_after_gc_hook’ called during thread startup leads to SIGSEGV

Previous Next

Full log

View this message in rfc822 format

From: ludo <at> gnu.org (Ludovic Courtès)
To: Andy Wingo <wingo <at> pobox.com>
Cc: 10655 <at> debbugs.gnu.org
Subject: bug#10655: [2.0.3+] ‘queue_after_gc_hook’ called during thread startup leads to SIGSEGV
Date: Mon, 30 Jan 2012 16:41:17 +0100

[Message part 1 (text/plain, inline)]

Hi!

I’m testing this patch:

[Message part 2 (text/x-patch, inline)]

diff --git a/libguile/gc.c b/libguile/gc.c
index 7816801..97dfcd8 100644
--- a/libguile/gc.c
+++ b/libguile/gc.c
@@ -730,14 +730,17 @@ queue_after_gc_hook (void * hook_data SCM_UNUSED,
   if (scm_debug_cells_gc_interval == 0)
 #endif
     {
-      scm_i_thread *t = SCM_I_CURRENT_THREAD;
-
-      if (scm_is_false (SCM_CDR (after_gc_async_cell)))
-        {
-          SCM_SETCDR (after_gc_async_cell, t->active_asyncs);
-          t->active_asyncs = after_gc_async_cell;
-          t->pending_asyncs = 1;
-        }
+      if (SCM_I_CURRENT_THREAD != NULL && SCM_I_CURRENT_THREAD->guile_mode)
+	{
+	  scm_i_thread *t = SCM_I_CURRENT_THREAD;
+
+	  if (scm_is_false (SCM_CDR (after_gc_async_cell)))
+	    {
+	      SCM_SETCDR (after_gc_async_cell, t->active_asyncs);
+	      t->active_asyncs = after_gc_async_cell;
+	      t->pending_asyncs = 1;
+	    }
+	}
     }
 
   return NULL;

[Message part 3 (text/plain, inline)]

Rationale:

  - With TLS, SCM_I_CURRENT_THREAD is never NULL but the whole struct,
    including ‘guile_mode’, is zero when the thread starts.

  - Without TLS, SCM_I_CURRENT_THREAD is NULL until ‘guilify_self_1’ has
    been called.

Thoughts?

(My “benchmark” has been running for some time already and the bug
hasn’t shown up again.)

Thanks,
Ludo’.

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.